Effects of bulk precipitation pH and growth period on cation enrichment in precipitation beneath the canopy of a beech ž Fagus moesiaca/ forest stand

The effects of bulk precipitation pH and growth period Žgrowing and dormant. on cation enrichment beneath foliage were examined in a beech ŽFagus moesiaca. forest stand during a 48-month period. The bulk precipitation pH values ranged from 4.2 to 7.2. The lowest values were observed in winter due to fossil fuel combustion in a nearby big city. The ratio of monthly ion fluxes of throughfall plus stemflow over monthly ion fluxes of bulk precipitation was chosen as an index of cation enrichment and, therefore, as the dependent variable. Bulk precipitation pH and growth period were chosen as independent factors. Precipitation interception Ž%. by tree canopies was also taken into account. It was found that the pH factor was significant only for H ion enrichment suggesting neutralization of H ions in the beech canopy, whereas Mg2 and K enrichment were greater in the growing period, probably as a result of leaching. Crown interception was negatively significant for NH 4 -N enrichment.